1. Field of the Invention
The present invention relates to a semiconductor device having a boosting circuit, in particular, a semiconductor device having a boosting circuit which supplies a potential higher than power source voltage.
2. Description of the Related Art
A boosting circuit is used for a variety of purposes, for example, for a CCD driver circuit, an organic EL driver circuit, a low-temperature polysilicon liquid crystal driver circuit, a white light emitting diode driver circuit, an RF circuit, and a multiple power source system. For example, reduction in voltage in a semiconductor device such as a flash memory is accompanied by boosting power source voltage for obtaining high voltage necessary for writing or erasing data. In recent years, a boosting circuit which has a small area and efficiently generates high voltage has been expected in various fields, with the higher integration of integrated circuits of semiconductor devices.
In order to reduce the area of a boosting circuit, use of a MOS capacitor using a semiconductor substrate having a conductivity type or an insulating film having high dielectric constant, as a capacitor (a capacitor element), is proposed (for example, Reference 1: Japanese Published Patent Application No. 2003-297936). In Reference 1, a semiconductor substrate having a conductivity type is used for one of electrodes of a MOS capacitor, and a conductive film corresponding to a gate electrode is used for the other of the electrodes, and an insulating film corresponding to a gate insulating film of a transistor is provided between the two electrodes to increase capacitance per unit area.